In a paper discharge mechanism of an image forming apparatus, especially when print paper such as thin paper with weak rigidity is discharged at time of high-speed printing, deformation such as rising of a tip end part of the paper across its full width or upward and rounded turning of both corner parts of the tip end of the paper may occur due to air resistance. Because of such deformation, the paper may lose its speed and drop so as to cover a discharge port, thereby causing problems specific to the thin paper, including paper discharge failure such as jam and deteriorated discharged paper alignment. Such problems occur remarkably on the first sheet of a print in particular.
Disclosed in Patent Literature 1 below is an invention of a paper discharge device intended to solve a problem that a tip end of paper such as thin paper with weak rigidity is caught by a paper discharge tray surface and a tip end part is thereby rounded. In this paper discharge device, the relationship between first and second nips N1 and N2 and the gently sloped surface 4b is set in order that paper discharge angles θa and θe formed by paper P discharged from the first nip N1 and the second nip N2 and a gently sloped surface 4b as a paper loading surface become favorable angles that do not cause paper rounding as a result of catching of the tip end of the paper P by the gently sloped surface 4b. Therefore, the paper discharge from the first nip N1 continues until reaching predetermined height Y1 that can maintain the favorable paper angles, and then upon switching of a paper discharge path to the higher-class second nip N2, the paper discharge from the second nip N2 starts at a favorable paper discharge angle for the topmost paper discharged from the first nip N1, which permits smooth discharge and loading of the paper up to height Y2 as a loading limit.